1. Field of the Invention
This invention relates to phenol derivatives having a phenol structure as part of the molecular backbone which are suitable for use as raw materials for the manufacture of heat-resistant thermosetting resins. The invention also relates to a process for producing such phenol derivatives.
2. Prior Art
Phenolic resins, urea resins and epoxy resins are well known thermosetting resins and because of their high heat resistance, good mechanical and electrical characteristics as well as good bonding properties, they are extensively used in various applications including adhesives, paints, semiconductor sealants, molding materials and binders. As the scope of their application is growing today, those thermosetting resins are required to satisfy more rigorous requirements for performance characteristics, particularly in terms of heat resistance, as well as water resistance and tenacity.
The heat resistance of most organic polymer materials is dependent on their molecular structure and it is generally held that the presence of aromatic and heterocyclic structures in their molecular backbone is advantageous for enhanced heat resistance. For example, Japanese Patent Publication (kokoku) No. Hei 6-18835 proposes the use of naphthalene compounds having a vinyl benzyl ether group to improve the heat resistance of polyimide resins. Japanese Patent Public Disclosure (kokai) No. Hei 6-93086 teaches that cured products of lesser weight loss by heating can be obtained by curing naphthalene and p-xylylene glycol in the presence of an acid catalyst.
These approaches share the common feature of being an attempt to provide enhanced heat resistance by introducing a comparatively large aromatic ring compound into the molecular backbone. However, no technologies have yet been established that can prepare the starting materials (naphthalene compounds and p-xylylene glycol) in an industrially advantageous manner and it is critical to establish economical methods of synthesis or develop alternatives for those compounds.
A problem that has recently been addressed in the use of semiconductor resins typified by ortho-cresol novolak epoxy resins is that they are so hygroscopic as to crack when dipped in a solder bath. To solve this problem, improvements in heat and water resistance are needed. Japanese Patent Public Disclosure (kokai) No. Sho 61-293219 proposed the epoxidization of phenolic resins modified with dicyclopentadiene, and Japanese Patent Public Disclosure (kokai) No. Hei 6-263839 proposed the epoxidization of dicyclopentadiene-modified naphtholic resins. However, neither products of epoxidization are satisfactory in terms of heat and water resistance and further improvements in these characteristics are desired.
Conventional thermosetting resins have the disadvantage of being "hard and brittle" on account of their molecular structure. With a view to eliminating this difficulty, attempts are being made to incorporate an aliphatic ring structure or to have a two-dimensional crosslinked structure introduced as part of the molecular backbone. However, it is difficult in the state of the art to introduce these structures and yet insure the desired heat resistance.
The present invention has been accomplished under these circumstances of the prior art of thermosetting resins and has as an object providing a starting material for the manufacture of thermosetting resins with improved heat resistance that have a reactive phenolic structure and a heat-resisting condensed polycyclic aromatic structure, as well as a process for producing said starting material in an industrially advantageous manner.
Another object of the invention is to provide a starting material for the manufacture of thermosetting resins having resistance to heat and water, as well as tenacity, or a modifier for imparting these desirable characteristics, and a process for producing said starting material or modifier in an industrially advantageous manner.
The present inventors made various studies on the reaction for copolymerizing condensed polycyclic aromatic hydrocarbons and phenols and found that in the presence of Friedel-Crafts catalysts, condensed polycyclic aromatic hydrocarbons easily reacted with phenols to provide copolymerization products having a phenolic structure and that by controlling the properties of those polymerization products, one could produce phenol derivatives in an industrially advantageous manner that had a phenolic structure as part of the molecular backbone and that were provided with suitable properties for use as starting materials for the manufacture of heat-resistant thermosetting resins. The present invention has been accomplished on the basis of these findings. The present inventors also found that when phenols were reacted with both condensed polycyclic aromatic hydrocarbons and unsaturated cyclic aliphatic hydrocarbons, one could produce phenol derivatives having suitable properties for use as either starting materials or modifiers that would provide thermosetting resins improved in terms of not only heat resistance but also water resistance and tenacity.